Question Definition
Follow up for “Unique Paths”:
Now consider if some obstacles are added to the grids. How many unique paths would there be?
An obstacle and empty space is marked as 1 and 0 respectively in the grid.
For example, There is one obstacle in the middle of a 3x3 grid as illustrated below.
[
[0,0,0],
[0,1,0],
[0,0,0]
]
The total number of unique paths is 2.
Note:
m and n will be at most 100.
Java Solution
public int uniquePathsWithObstacles(int[][] obstacleGrid) {
int m = obstacleGrid.length;
int n = obstacleGrid[0].length;
obstacleGrid[0][0]^=1;
for(int i = 1;i<m;i++){
obstacleGrid[i][0]=(obstacleGrid[i][0]==1)? 0:obstacleGrid[i-1][0];
}
for(int j = 1;j<n;j++){
obstacleGrid[0][j] =(obstacleGrid[0][j]==1)? 0: obstacleGrid[0][j-1];
}
for(int i = 1;i<m;i++){
for(int j =1;j<n;j++){
obstacleGrid[i][j] =(obstacleGrid[i][j]==1)? 0: obstacleGrid[i-1][j]+obstacleGrid[i][j-1];
}
}
return obstacleGrid[m-1][n-1];
}
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